Valsartan is a nonpeptide, orally active, and specific angiotensin II receptor blocker acting on the AT1 receptor subtype. Angiotensin II interacts with specific receptors on the surface of a target cell. It has been possible to identify receptor subtypes which are termed, e.g., AT1- and AT2-receptors. Significant efforts have been made to identify substances that bind to the AT1-receptor. Such active ingredients are often termed angiotensin II antagonists. Because of the inhibition of the AT1-receptor, such antagonists can be used, e.g., as antihypertensives or for the treatment of congestive heart failure. Angiotensin II antagonists are therefore understood to be those active ingredients which bind to the AT1-receptor subtype. Prolonged and uncontrolled hypertensive vascular disease ultimately leads to a variety of pathological changes in target organs such as the heart and kidney. Sustained hypertension can lead an increased occurrence of stroke.
Valsartan is chemically described as N-(1-oxopentyl)-N-[[2′-(1H-tetrazol-5-yl)[1,1′-biphenyl]-4-yl]methyl]-L-valine. Valsartan is used for treating hypertension, treatment of heart failure and reduction of cardiovascular mortality in clinically stable patients with left ventricular failure or left ventricular dysfunction following myocardial infarction.
Valsartan is typically administered as a solid oral dosage form such as, for example, tablets, pills, and capsules. Oral ingestion is the most convenient and commonly employed route of drug delivery due to its ease of administration, high patient compliance, cost effectiveness, reduced sterility constraints, and flexibility in the design of dosage form.
However, some patients, specifically pediatric and geriatric patient populations, may dislike or have difficulty swallowing solid oral dosage forms, which can lead to associated disadvantages, such as patient non-compliance. In such situations, oral liquid dosage forms, including solutions, suspensions and emulsions, can be easier to administer and more suitable for use.
Many marketed pharmaceutical products do not have regulatory approval for pediatric use, resulting in “off-label” prescribing by physicians. When a pharmaceutical product does not have a labeled indication for children, manufacturers do not produce strengths and dosage forms appropriate for the pediatric population. Extemporaneously-prepared formulations are a sub-optimal option in instances where commercial liquid formulations are not available. At present, liquid dosage forms for valsartan are prepared by compounding tablets into a suspension. However, developing and compounding of pediatric formulations can be challenging for dispensing pharmacists, resulting in a variety of issues, including inaccurate dosing, poor stability, poor taste, adherence problems, and lack of standardizations in extemporaneous compounding. Consumers requiring a liquid dosage form may be putting themselves at risk since the product may not be made consistently from one pharmacist to another. Further, extemporaneously-prepared valsartan formulations have a short shelf life, typically a maximum shelf life of only 90 days.
Poor bioavailability of pharmaceuticals presents a major challenge in designing oral dosage forms. The oral bioavailability depends on several factors, including aqueous solubility, drug permeability, dissolution rate, first-pass metabolism, presystemic metabolism, and susceptibility to efflux mechanisms. The most frequent causes of low oral bioavailability are attributed to poor solubility and low permeability. For orally administered drugs, solubility is the most important rate limiting parameter to achieve their desired concentration in systemic circulation for pharmacological response. Accordingly, liquid compositions containing active pharmaceutical ingredients that are completely solubilized in a liquid composition are more advantageous over suspension compositions. The extent of solubility of a substance in a specific solvent is measured as the saturation concentration, at which the addition of more solute does not increase its concentration in the solution. The extent of solubility ranges widely, from infinitely soluble (fully miscible) (for example, ethanol in water) to poorly soluble (for example, silver chloride in water). Solubility is based on the highest-dose strength of an immediate release product. A drug is considered highly soluble when the highest dose strength is soluble in 250 mL or less of aqueous media over the pH range of 1 to 7.5.
Accordingly, there remains a need for a highly bioavailable, highly soluble, stable valsartan oral solutions that can address these problems, while safely and effectively providing valsartan to patients who have difficulty swallowing solid dosage forms the proper and consistent administration of valsartan with accuracy and precision.